Adsorption of Phenol and Nitrophenol Isomers onto Montmorillonite Modified with Hexadecyltrimethylammonium Cation

Abstract

ABSTRACT Single- and two-component competitive adsorptions were carried out in a batch adsorber to investigate the adsorption behavior of phenol and 2-, 3-, and 4-nitrophen-ols in aqueous solution at 25°C onto hexadecyltrimethylammonium (HDTMA)-treated montmorillonite. HDTMA cation was exchanged for metal cations on the montmorillonite to prepare HDTMA—montmorillonite, changing its surface property from hydrophilic to organophilic. Effective solid diffusivity of HDTMA cation in the montmorillonite particle was estimated to be about 3 × 10−12 cm2/s by fitting the film-solid diffusion model to a set of HDTMA adsorption kinetic data onto mont-morillonite. Adsorption affinity on HDTMA—montmorillonite was found to be in the order 3-nitrophenol = 4-nitrophenol > 2-nitrophenol > phenol. The Langmuir and the Redlich—Peterson (RP) adsorption models were used to analyze the single component adsorption equilibria. The ideal adsorbed solution theory (IAST) and the Langmuir competitive model (LCM) were used to predict the multicomponent competitive adsorption equilibria. These models yielded favorable representations of both individ-ual and competitive adsorption behaviors.